Imaging Lens and Camera Module

ABSTRACT

Provided is an imaging lens and a camera module, the device including in an orderly way from an object side, a first lens with positive (+) refractive power; a second lens with negative (−) refractive power; a third lens with negative (−) refractive power; a fourth lens with negative (−) refractive power; and a fifth lens with negative (−) refractive power, wherein the lens is concavely formed at an object side surface.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 U.S.C. §119 of KoreanApplication No. 10-2009-0124183, filed on Dec. 14, 2009, which is herebyincorporated by reference in its entirety.

BACKGROUND OF THE DISCLOSURE

1. Field of the Invention

The present invention relates to an image lens and a camera module, andin particular, to an image lens for an image lens adequate for a cameramodule using a high-resolution image sensor and the camera module.

2. Discussion of the Related Art

Recently, vigorous research efforts are being made in the field of amobile phone-purpose camera module, a digital still camera (DSC), acamcorder, and a PC camera (an imaging device attached to a personcomputer) all connected with an image pick-up system. One of the mostimportant components in order that a camera module related to such animage pickup system obtains an image is an imaging lens producing animage.

Previously, there have been attempts to construct an imaging lens ofhigh-resolution by using 5 pieces of lenses. Each of 5 pieces of lensesis comprised of lenses with a positive (+) refractive power and lenseswith a negative (−) refractive power. For example, an imaging lens isconstructed on a structure of PNNPN (+−−−+−), PNPNN (+−+−−) or PPNPN(++−+−) in order starting from an object side. However, an imagingmodule of such a framework fails to show approving optic characteristicsor aberration characteristics. Accordingly, a high-resolution imaginglens of a new power structure is required.

BRIEF SUMMARY

The present invention provides an imaging lens and a camera lens havinga new power structure, especially, it provides an imaging lens and acamera module excellent in aberration characteristic.

An image lens according to one embodiment of the present inventioncomprises a first lens having positive (+) refractive power, a secondlens having negative (−) refractive power, a third lens having negative(−) refractive power, a fourth lens having negative (−) refractivepower, and a fifth lens having negative (−) refractive power in anorderly way from an object side, wherein the third lens is concavelyformed about an object side surface.

An imaging lens according to the present embodiment is formed of a lensin which a first lens has positive (+) power, and a second through afifth lenses has negative (−) power, and it provides an imaging lens,that is, a power structure of PNNNN. An imaging lens superb inaberration characteristic may be realized.

A camera module of the invention comprises a lens group including afirst lens having positive (+) refractive power, a second lens havingnegative (−) refractive power and a third through a fifth lenses beingall aspheric planes at an object side and an imaging side, in an orderfrom the object side; a filter transmitting light visible rays andreflecting infrared from light passed through the lens group; and alight reception device receiving light visible rays passed through thefilter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a construction diagram of an imaging lens according to thepresent embodiment;

FIG. 2 is a graph showing aberration characteristic according to oneembodiment of the present invention; and

FIG. 3 is a graph showing Coma aberration according to one embodiment ofthe present invention.

DETAILED DESCRIPTION

Since the present invention can be applied with various changes theretoand have several types of embodiments, specific embodiments intend to beexemplified in the drawings and minutely described in the detaileddescription. However, it does not limit the present invention to aspecific example but should be appreciated to include all the changes,equivalents and replacements which fall in the spirit and technicalscope of the present invention.

Stated that any component is “connected” or “conjunctive” to anothercomponent, it will be appreciated to be directly connected orconjunctive to the very another component or otherwise that there existsany component in the midst of them.

In the following, the present invention will be described in detailreferring to the attached drawings, but without regard to a drawingsign, an identical or corresponding component is assigned the samereference numeral and a redundant description regarding this will beomitted.

As a construction diagram of a camera lens module according to thepresent embodiment, FIG. 1 is a lateral surface construction diagramexemplifying a layout state of a lens around an optical axis ZO. In theconstruction of FIG. 1, a thickness, size, and shape of a lens arerather overdrawn for description, and a spheric or aspheric shape hasbeen only presented as one embodiment, but obviously not limited to thisshape.

Referring to FIG. 1, an imaging lens of the present invention has alayout construction with a first lens 10, a second lens 20, a third lens30, a fourth lens 40, a fifth lens 50, a filter 60, and a lightreceiving element 70 in an order from an object side.

Light corresponding to image information of a subject passes through thefirst lens 10, the second lens 20, the third lens 30, the fourth lens40, the fifth lens 50, and the filter 60 to be incident on the lightreceiving element 70.

Hereinafter, in description of a construction of each lens, “object sidesurface” means a surface of a lens facing an object side to an opticalaxis, and “image side surface” means a surface of a lens facing an imagesurface to an optical axis.

A first lens 10 has positive (+) refractive power and its object sidesurface S1 is convexly formed. An object side surface S1 of a fourthlens 10 may act as an aperture, and in this case, an imaging lens of thepresent embodiment may not need an additional aperture. Also, anaperture 20 is negative (−) refractive power, and its object sidesurface S3 is concavely formed.

A third lens 30, a fourth lens 40 and a fifth lens 50 are allconstructed of an aspheric face at an object side surface and an imagingside surface. A third lens 30 and a third lens 40 have negative (−)refractive power, and a fifth lens 50 has a refractive power in negativevalue.

As shown in the figure, a third lens 30 is a meniscus form being anobject side surface S5 concavely formed. The fourth lens 40 is ameniscus form in which an object side surface S7 is concavely formed,and a fifth lens 50 is a meniscus form in which an object side surfaceS9 is convexly formed.

Here, a fifth lens 50 is an aspheric form in which both surfaces of anobject side surface S9 and an imaging side surface S10 are all giveninflection points. As shown in the figure, an imaging side surface S10of a fifth lens 50 is bent towards an imaging side as heading from acentral part which is centered on an optical axis ZO to a surrounding,and again forms an aspheric inflection point by bending into an objectside as marching from a surrounding part which is far away off anoptical axis ZO to an outermost angle area.

An aspheric inflection point formed at a fifth lens 50 may adjust amaximum emergence angle of a primary ray incident on a light receivingelement 70. And, an aspheric inflection point formed at an object sidesurface S9 and an object side surface S10 of a fifth lens 40 adjusts amaximum emergence angle of a primary ray, and inhibits a shading of asurrounding part of a screen.

The filter 60 is at least any one of optical filters such as an infraredfilter and a cover glass. A filter 40, in a case an infrared filter isapplied, blocks such that radiating heat emitting from external lightdoes not transfer to the light receiving element 70. Also, an infraredfilter penetrates visible light and reflects infrared for outflow to anexternal part.

The light receiving element 70 is an imaging sensor such as CCD (ChargeCoupled Device) or CMOS (Complementary Metal Oxide Semiconductor).

The first lens 10, the second lens 20, the third lens 30, the fourthlens 40 and the fifth lens 50 use an aspheric lens like alater-described embodiment, thereby improving resolution of a lens andtaking an advantage of superior aberration characteristic.

A later-described conditions and embodiment is a preferred embodimentraising an action and effect, and it would be understood by a person inthe art that the present invention should be constructed of thefollowing conditions. For example, a lens construction of the inventionwill have a raised action and effect only by satisfying part ofconditions among lower-part described condition equations.

0.5<f1/f<1.5  [Condition 1]

0.5<T/f<1.5  [Condition 2]

1.6<N2<1.7  [Condition 3]

20<V2<30  [Condition 4]

where, f: overall focal length of imaging lens

f1: focal length of first lens

T: distance from object side surface of first lens to image-formingsurface

N2: refractive index of second lens

V2: Abbe value of second lens

Condition 1 specifies refractive power of a first lens 10. The firstlens 10 has a refractive power having proper spherical aberration andproper chromatic aberration corrected by Condition 1. Condition 2specifies a dimension of an optical axis direction of an overall opticalsystem, that is, defines a subminiature lens related condition and aproper aberration correction related condition.

Condition 3 specifies reflective index of a second lens 20, andCondition 4 specifies Abbe number of a second lens 20. Specification ofreflective index and Abbe number of each lens is conditions forsatisfactorily correcting chromatic aberration.

Hereinafter, an action and effect of the present invention will bepresented with reference to a specific embodiment. An aspheric shapementioned in the following embodiment is obtained from a known Equation1, where k denotes Conic constant and ‘E and its continuing number’ usedin aspheric coefficient A, B, C, D, E, F denotes power of 10. Forexample, E+01 indicates 10¹, and E-02 indicates 10⁻².

$\begin{matrix}{z = {\frac{{cY}^{2}}{1 + \sqrt{1 - {\left( {1 + K} \right)c^{2}Y^{2}}}} + {AY}^{4} + {BY}^{4} + {CY}^{4} + {DY}^{4} + {EY}^{4} + {FY}^{4} + \ldots}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

where, z: distance in optical axis direction from top point of lens

c: basic curvature of lens

Y: distance in perpendicular direction to optical axis

K: Conic constant

A, B, C, D, E, F: aspheric coefficient

Embodiment

The following Table 1 shows an embodiment complying with theabove-described Condition.

TABLE 1 Embodiment f 5.78 f1 3.36 f2 −6.84 f3 −100 f4 −100 f5 −100 f1/f0.58 T 6.44 T/f 1.11 N2 1.62 V2 26

Referring to Table 1, f1/f is 0.581, so that it can be known to matchwith Condition 1, T/f is 1.11, and thus matching to Condition 2 can beknown. Also, refractive index N of a second lens 20 complies withCondition 3, and it can be appreciated that Abbe number V2 of a secondlens 20 matches to Condition 4.

An embodiment of Table 2 shows a more specific embodiment over anembodiment of Table 1.

TABLE 2 Curvature Surface Radius Thickness Refractive number (R) orDistance (d) index (N) 1* 1.9 0.70 1.59 2* 22.7 0.20 3* −13.1 0.40 1.614* 6.4 0.44 5* −16.6 0.56 1.53 6* −24.4 0.76 7* −1.7 0.70 1.53 8* −2.00.10 9* 2.3 0.85 1.53 10*  1.9 0.56 11  0.30 1.52 12  0.88 image −0.02

In the above Table 2 and the following Table 3, notation * stated nextto surface numbers indicates an aspheric surface.

The following Table 3 indicates a value of an aspheric coefficient ofeach lens in an embodiment of the Table 2.

TABLE 3 Surface Number k A B C D E F  1* 0.031132 0.530590E−0 0.454248E−02 −0.977041E−03  0.112390E−02 −0.763141E−04  2* 0 0.138110E−02 −0.242609E−02 −0.183146E−02 −0.229414E−02  0.141290E−02 3* 0 −0.470439E−02 −0.681563E−02 −0.145754E−02  0.240966E−02−0.141168E−03  4* 0  0.144273E−01  0.742174E−02  0.307285E−02 0.109284E−02  0.728490E−02  5* 0 −0.109635E−01 −0.263756E−02 0.627748E−03  0.268656E−02 −0.381210E−03  6* 0  0.114874E−01−0.207353E−02  0.353580E−02  0.212405E−02 −0.425894E−03  7* −8.247871−0.842418E−01 −0.639694E−02  0.108078E−01 −0.440222E−03 −0.190031E−03 8* −0.234956 −0.145469E−01 −0.137677E−02  0.375517E−02  0.973959E−03−0.374778E−03  9* −1.438254 −0.133117E+00  0.498423E−01 −0.105833E−01 0.122936E−02 −0.587350E−04 −0.657907E−06 10* −3.754230 −0.636660E−01 0.190847E−01 −0.370502E−02  0.393843E−03 −0.185263E−04 −0.636154E−09

As a graph measuring coma aberration, FIG. 2 is a graph measuringtangential aberration and sagittal aberration of each wavelength basedon a field height.

In FIG. 2, as a graph showing a test result approaches to an X axis at apositive axis and a negative axis, respectively, it is explained that acoma aberration correction function is good. In measurement examples ofFIG. 2, a value of images in nearly all fields appear proximate to an Xaxis, it is explained that all of them show a superior commaticaberration correction function.

In FIG. 2, a Y axis means size of an image, and an X axis means focaldistance (unit: mm) and distortion degree (unit: %). In FIG. 2, it isinterpreted that an aberration correction function is good as curvesapproach to the Y axis. In a shown aberration diagram, because a valueof images in nearly all fields appears proximate to the Y axis, andlongitudinal spherical aberration, astigmatic field curves, anddistortion all show a superior figure.

As a graph measuring coma aberration, FIGS. 3 a and 3 b are graphsmeasuring tangential aberration and sagittal aberration of eachwavelength based on a field height. In FIGS. 3 a and 3 b, as a graphshowing a test result approaches to an X axis at a positive axis and anegative axis, respectively, it is explained that a coma aberrationcorrection function is good. In measurement examples of FIG. 3, a valueof images in nearly all fields appear proximate to an X axis, it isexplained that all of them show a superior commatic aberrationcorrection function.

While the present invention has been described with reference toembodiments in the above part, it would be understood by those skilledin the art that various changes and modifications can be made withoutdeparting from the spirit or scope of the present invention. Therefore,not confined to the above-described embodiment, the invention would beasserted to include all embodiments within the scope of the accompanyingclaims.

1. An imaging lens, comprising in an orderly way from an object side: afirst lens with positive (+) refractive power; a second lens withnegative (−) refractive power; a third lens with negative (−) refractivepower; a fourth lens with negative (−) refractive power; and a fifthlens with negative (−) refractive power, wherein the lens is concavelyformed at an object side surface.
 2. The imaging lens of claim 1,wherein the third lens, the fourth lens and the fifth lens are allimaging lenses having aspheric faces at an object side surface and animaging side surface.
 3. The imaging lens of claim 1, wherein the fourthlens is concavely formed at an object side surface.
 4. The imaging lensof claim 1, wherein the fifth lens is convexly formed at an object sidesurface.
 5. The imaging lens of claim 4, wherein the fifth lens isformed with an inflection point at each of an object side surface and animaging side surface.
 6. The imaging lens of claim 5, wherein theinflection point is an aspheric inflection point.
 7. The imaging lens ofclaim 1, wherein the third lens, the fourth lens and the fifth lens arelenses of a meniscus form.
 8. The imaging lens of claim 1, wherein whenan overall focal length of the imaging lens is f, and a focal length ofthe first lens is f1, the imaging lens satisfies a condition of0.5<f1/f<1.5.
 9. The imaging lens of claim 1, wherein the imaging lenssatisfies a condition of 0.5<T/f<1.5, when an overall focal length ofthe imaging lens is f, and a distance from an object side surface of thefirst lens to an image-forming surface is T.
 10. The imaging lens ofclaim 1, wherein the imaging lens satisfies a condition of 1.6<N2<1.7,when a refractive power of the second lens is N2.
 11. The imaging lensof claim 1, wherein the imaging lens satisfies a condition of 20<V2<30,when an Abbe number of the second lens is V2.
 12. A camera modulecomprising: a lens group including a first lens having positive (+)refractive power, a second lens having negative (−) refractive power anda third through a fifth lenses being all aspheric planes at an objectside and an imaging side, in an order from the object side; a filtertransmitting light visible rays and reflecting infrared from lightpassed through the lens group; and a light reception device receivinglight visible rays passed through the filter.
 13. The camera module ofclaim 12, wherein the third through fifth lenses have negative (−)refracting power.
 14. The camera module of claim 12, wherein the thirdlens is concave at the object side.
 15. The camera module of claim 12,wherein the third lens through the fifth lens are all aspheric planes atthe object side and at an imaging side.
 16. The camera module of claim1, wherein the fourth lens is concavely formed at the object side, andthe fifth lens is convexly formed at the object side.
 17. The cameramodule of claim 1, wherein the fifth lens has all aspheric inflectionpoints at the object side surface and an imaging side surface.
 18. Thecamera module of claim 1, wherein the camera module satisfies acondition of 0.5<f1/f<1.5, when an overall focal distance of the lensgroup is f, and a focal distance of the first lens is f1.
 19. The cameramodule of claim 1, wherein the camera module satisfies a condition of0.5<T/f<1.5, when an overall focal distance of the lens group is f, anda distance from the object side to an image-forming surface of the firstlens is T.
 20. The camera module of claim 1, wherein the camera modulesatisfies a condition of 1.6<N2<1.7, when a refractive index of thesecond lens is N2.